Method of recharging a rechargeable battery

ABSTRACT

This invention relates to a method for recharging a chargeable battery for a motor vehicle, a machine, a motor boat or the like. As the charging voltage there is used the output voltage from a charging generator which is connected to the battery, the output voltage being varied by controlling the field of the generator. The charging takes place by means of repeated charging cycles each of which consists of a charging period and a test period when the battery is loaded and the charging from the generator to the battery is disconnected. The value of the charging voltage during a charging period is determined on the basis of the test result during the immediately preceding test period. According to the invention the battery voltage is compared to a pre-determined voltage during each test period. If the comparison shows that the battery voltage is less than the pre-determined voltage or drops below this voltage during the test period, the charging of the battery during the following charging period takes place at a charging voltage which is sufficiently high that, by controlling the output voltage of the generator, there is rapid charging of the battery. If the comparison shows that the battery voltage is higher than the pre-determined voltage the charging during the following charging period takes place at a charging voltage which provides a compensating charging of the battery. During the later part of the charging period, just before the test period, the charging always takes place at a charging voltage corresponding to the compensating charge.

This invention relates to a method for recharging a chargeable batteryfor a vehicle, a machine, a motor boat or the like, whereby the outputvoltage from a battery charging generator connected to the battery isused as a charging voltage the magnitude of which can be varied bycontrolling the field of the generator and whereby the recharging isperformed by means of repeated charging cycles each of which consists ofa charging period and a test period during which the battery is loadedand the charging from the generator to the battery is disconnected. Themagnitude of the charging voltage during a charging period is determinedwith regard to the test result achieved during the immediately precedingtest period. The invention also relates to a charging regulator forrecharging of a rechargeable battery for a motor vehicle, a machine, amotor boat or the like, said regulator being connected to a line betweenthe battery and a battery recharging generator of a type in which theoutput voltage thereof can be varied by varying the magnetizing currentof the generator. During repeated charging cycles each of which consistsof a test period and a charging period, the regulator interrupts thecharging during each test period while the battery is loaded in order tomeasure the charging condition of the battery and to control the outputvoltage of the generator during the next following charging period,depending on the detected charging condition.

In recent years battery run electrical equipment such as, for example,refrigerators, heaters and radio equipment has become more and morecommon in, for example, long distance trucks and motor boats. As suchequipment consumes a substantial current compared with the equipmentthat was previously conventional, the new equipment produces a biggerload on the battery, especially as the generator and its regulator aredesigned to provide current only when the engine that drives thegenerator, as well as the vehicle or boat, is running. If the engine hasnot been running for a couple of hours while one or more of the aboveitems of equipment has been connected, the battery is normally more orless discharged.

In accordance with one aspect of the present invention there is provideda method for recharging during operation a chargeable battery connectedto an electrical system of a motor vehicle, a machine, a motor boat orthe like wherein the output voltage from a generator connected to thebattery is used as a charging voltage the amplitude of which can bevaried by controlling the field of the generator, and wherein therecharging is performed by one or repeated charging cycles during whichthe charging is performed at a raised charging voltage which, bycontrolling the output voltage of the generator, is just below the upperlimit of the range of operating voltage of the electrical system.

In accordance with a further aspect of the present invention there isprovided a voltage regulator for recharging during operation arechargeable battery which is connected to an electrical system of amotor vehicle, a machine, a motor boat or the like, said regulator beingconnected to a line between the battery and a generator having an outputwhich can be varied by varying the magnetizing current of the generator,wherein the regulator comprises a control device arranged to definecyclic charging periods of equal time during which, by controlling themagnetizing current of the generator, there is applied to the battery anincreased voltage which is just below the upper limit voltage value ofthe electrical system.

Other features and characteristics of the present invention will beobvious from the following specification in conjunction with theenclosed drawings in which:

FIG. 1 is a block diagram showing a conventional charging regulatorsystem;

FIG. 2 which corresponds to FIG. 1 illustrates a charging regulatorsystem according to the present invention;

FIG. 3 is a flow chart which shows how a charging regulator according tothe invention functions;

FIGS. 4-6 show by a dotted and a continuous line, respectively, howcharging current, charging voltage and charging quantity varies withtime when using a conventional charging voltage regulator and aregulator according to the invention, respectively, and

FIG. 7 is a block diagram showing the principal design of a chargingregulator according to the invention.

FIG. 1 shows schematically in the form of a block diagram how a battery1, a generator 2 and a charging regulator 3 are internally electricallyconnected in a conventional charging regulator system having a negativeearth to be used, for example, in a motor vehicle. The positive pole 4of the battery 1 is connected to the charging output 5 of the generator2 and is also connected, via an ignition key switch 6, to one terminalof a charging light 7, the other terminal of which is connected to theregulator voltage output 8 of the generator 2. This other terminal ofthe light 7 is also connected to the supply- and measuring input 9 ofthe regulator 3. A line 10 connects the regulator output 11 of theregulator 3 with the field winding input 12 of the generator 2.

When the ignition key switch 6 is closed as the engine is started, thebattery is connected to the regulator 3 and hence to the field windingof the generator 2. Before the charging commences, current flows fromthe battery 1 to the regulator 3. This current passes through thecharging lamp 7, which is thus lit. When the generator 2 is rechargingthe battery 1, the voltage of the output 8 is equal to the batteryvoltage. At this time there is no current flow through the charginglight 7, which consequently is not lit. The regulator 3 operates in sucha manner that by detecting the voltage at the output 8 it controls thegenerator field so that the output voltage of the generator 2, i.e. itscharging voltage, has a pre-determined value. When the input voltage ofthe regulator is less than this voltage value, the battery is completelyrecharged. The charging ceases when the input voltage reaches saidvalue.

It will be appreciated that recharging of the battery 1 with theabove-described conventional charging regulator system is not achievedin the expected manner if the generator runs at a low speed, if theconnections between the generator 2 and the battery 1 are in poorcondition, or if the charging ability of the battery 1 is reduced. Atlow speed of the generator 2 no more charging is achieved than thatwhich is needed for the charging light 7 to go off, and one is misledinto believing that the charging is working perfectly when in realityperhaps only a few amperehours have been added to the battery 1 althoughthe engine has been working for a considerable time. It is very commonfor the conductors, the connections between the conductors and the polesof the battery 1 and battery master switch to be in poor condition whichcauses a potential drop. Since the regulator 3 detects the voltage atthe generator 2, and not at the battery, the charging voltage may be asmuch as 1 V less than the predetermined charging voltage at low chargingamperages. This causes minimal or no charging of the battery 1. Theconventional regulator 3 also controls the output voltage of thegenerator 2 so that this has a constant value which is independent ofthe charging ability of the battery. This also results in the effectivecharging being very poor with an extremely discharged battery.

The object of the present invention is to provide a method of, and acharging regulator for, recharging a rechargeable battery in which themethod and regulator do not have above disadvantages. This object isachieved by the invention having the characteristics recited in theappended claims.

In FIG. 2 in which the same reference numbers as in FIG. 1 are usedwhere applicable, 13 denotes a charging regulator according to thepresent invention. Apart from the output 11, which is identical to thatof the regulator 3, the regulator 13 has four inputs 14, 15, 16 and 17.The input 14 is connected to the regulator voltage output 8 of thegenerator and is arranged to receive a starting signal from thegenerator 2 showing that the generator is working and is generating acharging voltage. The input 15 which is connected to the charging output5 of the generator and to the positive pole 4 of the battery 1 can becompared with the input 9 of the regulator 3 which is a feed- and testsignal input. The input 16 is directly connected to the positive pole 4of the battery 1 and is therefore the test signal input for the batteryvoltage, and the input 17 which is connected to the positive pole 4 ofthe battery 1 via the ignition key switch 6 and the charging light 7 canalso be considered as a starting signal input the function of which canlikewise be compared to that of the input 9 of the regulator 3.

The regulator 13 according to the invention differs from theconventional regulator 3 in the following respects: By way of thecharging light 7 or any other acoustic or optic alarm means, a warningis provided when the generator 2 does not reach its working voltage as aresult of operating at too low a speed. It also provides a warning ifthe potential drop between the generator 2 and the battery 1 isunacceptably high. The charging voltage and therefore also the chargingcurrent to the battery 1 is regulated with respect to the condition ofthe battery. The charging is carried out by means of repeated chargingcycles each of which consists of a charging period, and a test periodwith the battery loaded. The charging voltage is determined on the basisof the test result. An extremely discharged battery cannot assimilatemaximum charging for an unlimited time, which is why there is also atime limit in order to protect the battery against this type ofovercharging.

It will now be explained in more detail how charging according to theinvention takes place with reference to the flow chart in FIG. 3. Arefers to the starting condition. The regulator commences to be fed withcurrent, via the input 15 and the charging programme is set at zero.Stage B represents a charging period during which a charging voltagewhich provides a compensating charge to the battery is applied to thebattery for a certain period of time (5 minutes). If a 12 V battery isused (which will be assumed to be the case in the following description)typical value for a compensating charge voltage is 14 V and the periodof time is 5 minutes. To achieve this, the battery voltage is comparedto a reference voltage and the regulator controls the field current ofthe generator so that said voltages are equalised. To check thecondition of the lead between the generator and the battery, the batteryvoltage is compared to another reference voltage (9 V), which isconsiderably smaller than the first said reference voltage. If thebattery voltage happens to be lower than the second reference voltagethe voltage detection of the regulator 13 is changed from the batterypole 4 to the charging output 5 of the generator 2. After the abovementioned time (5 minutes) has lapsed the regulator programme switchesover to C.

Stage C is a measuring phase. The battery voltage is measured for acertain period of time (1 minute) but is cut off if the battery voltagedrops below a certain voltage (13.2 V) before the time is ended. Whilemeasuring, all alarms are blocked, and the charging of the battery iscut off by cutting the field current of the generator 2. It is presumedthat the battery is loaded while measuring. This is automatically thecase with cars where the head lights or other equipment of the typehereinbefore referred to is switched on. The measuring of the batteryvoltage takes place by comparing it to the said reference voltage. Ifthe battery voltage is equal to or less than the reference voltage, theprogramme continues to D. If the battery voltage is higher than thereference voltage the programme continues to F. At D the battery ischarged with a charging voltage (14.6 V) for a certain period of time (8minutes) which is equal to quick charging of the battery. The said time,however, is counted from the moment the voltage exceeds a certain value(14.4 V), whereby a charging time which takes into consideration thecapacity of the battery is achieved. In other words D comprises thecharging phase which also applies to E.

During stage E charging takes place with a voltage (14 V) related to thecompensating charge for a time (2 minutes) which is shorter than thetime of stage D. Thereafter the charging programme switches to C.

If the battery voltage is higher than the first reference voltage thecharging programme of the regulator switches to F.

Stage F is a compensating charging phase which takes place for acomparatively long time (1-3 hrs). After this the programme switches toB.

It can be observed that the sequence consisting of C, D and E providesquick charging of the battery, while the sequence including C, F and Bprovides a compensating charging of the battery.

Stage G represents the different test measurements or comparisons whichare carried out according to the invention and which have previouslybeen partly explained. In this stage the battery voltage and thegenerator voltage are continuously compared to the reference voltages todetermine overvoltage, undervoltage or unacceptable potential drops inthe lead between the generator and the battery.

In FIG. 4 the programme stages A, B, C, D and E are again shown. Inrelation to charging current as well as charging voltage and amount ofcharging, the graphs (continuous) showing charging according to theinvention are all above those (dotted) which represent a conventionalsystem of charging.

Although it is obvious that a man skilled in the art, having knowledgeof how a charging regulator according to the invention functions, canmake this invention in a number of ways, one example of the inventionwill be explained in the following, referring to the block diagram shownin FIG. 7. While for simplicity the invention is described withreference to FIG. 7 in a rather general manner, in practice the wholeregulator is preferably constructed on one so-called IC circuit withwhich further test and control functions outside the scope of thepresent invention can be achieved, if so desired.

In FIG. 7 the battery 1, the generator 2 and, within a dotted outline,the regulator 3 are again shown. Numeral 18 denotes a control unit theinputs of which are connected to a comparator 19, a clock 20 consistingof an oscillator, and a binary counter, arranged to generate controlpulses to control all time lapses in the control unit 18, and a counter21. The outputs of the control unit 18 are connected to a referencevoltage source 22 arranged to generate the previously described saidreference voltages, to the generator 2, to the clock 20, to the counter21 and to the load 23. The inputs of the comparator are connected to thereference voltage source 22, the generator 2 and the battery 1. Apartfrom said connection to one of the inputs of the control unit the outputof the comparator 19 is connected to an alarm device 24 arranged toprovide an optic and/or acoustic alarm.

A temperature detector 25 thermally connected to the battery 1 isarranged to generate a signal related to the temperature of the batteryand to control the reference voltage source 22 with this signal, so thatall reference voltages and thereby also the battery charging voltage areincreased with a decreasing battery temperature. The opposite takesplace with an increasing battery temperature.

The comparator 19 includes a number of comparing circuits arranged tocompare the reference voltages from the reference voltage source 22 withthe generator- and battery voltages as described previously. As a resultof these comparisons control signals are generated to the control unit18 and alarm signals are generated to the alarm device 24. This isarranged to provide warnings with different characteristics fordifferent errors so that these can be easily identified.

The control unit 18 is arranged to control the generator voltage, in themanner that is characteristic of the invention, governed by inputs fromthe comparator 19, the clock 20 and the counter 21. If the battery 1 isnot sufficiently loaded during the measuring phase, which is often thecase with diesel engine driven motor boats, the load 23 is automaticallyswitched on. The number of charging cycles when charging takes place ata voltage related to quick charging is counted by the counter 21, whichis arranged to provide a switch off signal to the control unit when apre-decided number of quick charging cycles (e.g. 8) has taken place.

I claim:
 1. Method for recharging during operation of a chargeablebattery (1) connected to an electrical system of a motor vehicle, aworking machine, a motor boat or similar, whereby an output voltage froma generator (2) connected to the battery (1), by way of a chargingcircuit, is used as a charging voltage the amplitude of which can bevaried by means of controlling the field of the generator (2),characterized in that, the recharging is performed by means of at leastone charging cycle during which charging is performed at a voltage levelsuitable for recharging the battery which is controlled by the outputvoltage of the generator (2), each charging cycle consists of a chargingperiod and a test period, and during the test period the battery (1) isloaded and the charging circuit from the generator (2) to the battery(1) is disconnected.
 2. Method for recharging during operation of achargeable battery (1) connected to an electrical system of a motorvehicle, a working machine, a motor boat or similar, whereby an outputvoltage from a generator (2) connected to the battery (1), by way of acharging circuit, is used as a charging voltage the amplitude of whichcan be varied by means of controlling the field of the generator (2),characterized in that, the recharging is performed by means of at leastone charging cycle during which charging is performed at a voltage levelsuitable for recharging the battery which is controlled by the outputvoltage of the generator (2), each charging cycle consists of a chargingperiod and a test period, during the test period the battery (1) isloaded and the charging circuit from the generator (2) to the battery(1) is disconnected, and the battery voltage is compared to apre-decided voltage, if the comparison shows that the battery voltage islower than the pre-decided voltage, or decreases to below this voltageduring the test period, recharging takes place during the followingcharging period at a suitable charging voltage and if the comparisonshows that the battery voltage is higher than the pre-decided voltage,the recharging during the following charging period takes place at acharging voltage which gives a compensating charge to the battery (1),and that during the later part of the charging period, immediatelybefore the test period, the charging always takes place at a chargingvoltage corresponding to the compensating charge.
 3. Method forrecharging during operation of a chargeable battery (1) connected to anelectrical system of a motor vehicle, a working machine, a motor boat orsimilar, whereby an output voltage from a generator (2) connected to thebattery (1) is used as a charging voltage the amplitude of which can bevaried by means of controlling the field of the generator (2),characterized in that, the recharging is performed by means of at leastone charging cycle during which charging is performed at a voltage levelsuitable for recharging the battery which is controlled by the outputvoltage of the generator (2), wherein recharging with a rapid chargingvoltage is carried out during at most a pre-decided number of chargingperiods and the recharging which takes place thereafter is at acompensating charge voltage.
 4. Method for recharging during operationof a chargeable battery (1) connected to an electrical system of a motorvehicle, a working machine, a motor boat or similar, whereby an outputvoltage from a generator (2) connected to the battery (1) is used as acharging voltage the amplitude of which can be varied by means ofcontrolling the field of the generator (2), characterized in that, therecharging is performed by means of at least one charging cycle duringwhich charging is performed at a voltage level suitable for rechargingthe battery which is controlled by the output voltage of the generator(2), during charging at a suitable charging voltage, each charging cycleduration is counted in effective charging time, that is, the periodduration is counted only under a presumption that the charging voltageexceeds a certain value.
 5. Voltage regulator for recharging duringoperation of a rechargeable battery (1), connected to an electricalsystem of a motor vehicle, a working machine, a motor boat or similar, aregulator (3) being connected to a line between the battery (1) and agenerator (2) of a kind an output of which can be varied by varying amagnetizing current of the generator (2), characterized in that theregulator (3) comprises a control device (18) arranged to define cycliccharging periods of equal time and to control the magnetizing current ofthe generator (2) applied to the battery (1) and to maintain a chargingvoltage to just below an upper limit voltage value of the electricalsystem, the control device (18) is arranged to insert test periodsbetween the charging periods, during the test periods the magnetizingcurrent of the generator (2) is momentarily interrupted while thebattery (1) is partially loaded.
 6. Voltage regulator for rechargingduring operation of a rechargeable battery (1), connected to anelectrical system of a motor vehicle, a working machine, a motor boat orsimilar, a regulator (3) being connected to a line between the battery(1) and a generator (2) of a kind an output of which can be varied byvarying a magnetizing current of the generator (2), characterized inthat the regulator (3) comprises a control device (18) arranged todefine cyclic charging periods of equal time and to control themagnetizing current of the generator (2) applied to the battery (1) andto maintain a charging voltage to just below an upper limit voltagevalue of the electrical system, a comparator (19) is arranged with aloaded battery (1) and the control device (18), the comparator (19) isconnected with the battery (1) and a reference voltage source (22), thecomparator (19) compares the battery voltage with a pre-decided voltagevalue, during the following charging period a charging voltage which isbig enough to be a compensating charge is applied to the battery (1) ifthe battery voltage has been found to be higher than the pre-decidedvoltage value, otherwise an increased voltage is applied to the battery(1) under a presumption that the comparator (19), during a test period,has found that the battery voltage is lower than said pre-decidedvoltage value.
 7. Voltage regulator for recharging during operation of arechargeable battery (1), connected to an electrical system of a motorvehicle, a working machine, a motor boat or similar, a regulator (3)being connected to a line between the battery (1) and a generator (2) ofa kind an output of which can be varied by varying a magnetizing currentof the generator (2), characterized in that the regulator (3) comprisesa control device (18) arranged to define cyclic charging periods ofequal time and to control the magnetizing current of the generator (2)applied to the battery (1) and to maintain a charging voltage to justbelow an upper limit voltage value of the electrical system, theregulator (3) includes a temperature detector (25) arranged on thebattery (1) and a reference voltage source (22) is arranged to stepwisevary the reference voltage value depending on an output from thetemperature detector (25), increasing the voltage value in proportion toa decreasing battery temperature and decreasing the voltage value inproportion to an increasing temperature.
 8. Voltage regulator forrecharging during operation of a rechargeable battery (1), connected toan electrical system of a motor vehicle, a working machine, a motor boator similar, a regulator (3) being connected to a line between thebattery (1) and a generator (2) of a kind an output of which can bevaried by varying a magnetizing current of the generator (2),characterized in that the regulator (3) comprises a control device (18)arranged to define cyclic charging periods of equal time and to controlthe magnetizing current of the generator (2) applied to the battery (1)and to maintain a charging voltage to just below an upper limit voltagevalue of the electrical system, the regulator (3) includes a countingdevice (21), arranged to count the number of consecutive chargingperiods where charging takes place at a charging voltage relating to arapid charging and to control the charging regulator (3) to add acompensating recharging voltage to the battery (1) for a comparativelylong time when said number exceeds a pre-decided number of chargingperiods.
 9. Method for recharging during operation of a chargeablebattery (1) connected to an electrical system of a motor vehicle, aworking machine, a motor boat or similar, whereby the output voltagefrom a generator (2) connected to the battery (1), by way of a chargingcircuit, is used as a charging voltage the amplitude of which can bevaried by means of controlling the field of the generator (2),characterized in that the recharging is performed by means of at leastone charging cycle during which the charging is performed at a voltagelevel suitable for recharging the battery by controlling the outputvoltage of the generator (2); each charging cycle consists of a chargingperiod and a test period during the test period the battery (1) isloaded and the charging circuit from the generator (2) to the battery(1) is disconnected; during the test period the value of the batteryvoltage is compared to a pre-decided voltage, that if the comparisonshows that the battery voltage is lower than the pre-decided voltage, ordecreases to below this voltage during the test period, the rechargingtakes place during the following charging period at a suitable chargingvoltage; and if the comparison shows that the battery voltage is higherthan the pre-decided voltage, the recharging during the followingcharging period takes place at a charging voltage which gives acompensating charge of the battery (1) and that during the later part ofthe charging period, immediately before the test period, the chargingalways takes place at a charging voltage corresponding to thecompensating charge.